The present invention relates generally to a method for reducing position uncertainty of a portable inertial navigation device.
A device used in a portable inertial navigation system (xe2x80x9cPINS devicexe2x80x9d) utilizes accelerometers, gyroscopes, and support electronics, such as a processor, in order to determine motion changes. These motion changes are then translated to a position based on a reference position and the integration or differentiation of the motion changes. As time progresses, the errors associated with the accelerometers and gyroscopes increases to a point where the PINS device provides a location of the user that is outside of the required positional resolution, thus rendering the device ineffective or lost.
Resolving this problem can take on many forms. One solution is to add beacons in the building, which allows for updates at specific locations. A problem with this solution is every building entered must be retrofitted in order to receive those updates.
Another solution common in the field is the use of triangulation using three or more radio frequency (xe2x80x9cRFxe2x80x9d) links. The problem with this solution is that the multi-path has a tendency to reduce resolution to unacceptable levels for in-building solutions.
Thus, there exists a need for ensuring that the required positional resolution is maintained for an indefinite period of time, without the need to recapture global positioning system (xe2x80x9cGPSxe2x80x9d) signals or the like.